The invention concerns a rearview mirror arrangement, especially a lightweight mirror assembly for commercial vehicles.
Outside mirrors of this kind and of variously different construction are already known in the present state of the technology. A mirror pane is adjustably affixed by a pivoting mechanism to a housing part, which part is appropriately connected to the body of the vehicle, allowing the mirror to swing in reference to the housing part. The housing part is, as a rule, a solid plastic part, produced by injection molding. It is generally of a basin-like construction in which further mirror components or corresponding connection points for additions are installed. In particular, for large truck and bus mirrors, the carrying structure for outside mirrors is based on tubing or plates, which are affixed directly to the mirror holder which projects toward the vehicle body. This construction is disclosed by EP-A-0 590 510. The housing part serves then as a covering of the back side of the mirror plate and supports the pivoting mechanism. The housing also provides a streamlined sheathing of the outside mirror. Such construction is extremely expensive and heavy.
A problem with this tube and plate construction is that relatively strong vibrations occur in the rearview mirror assembly during the operation of the vehicle. In order to reduce these vibrations, EP 0 865 967 A2 proposes a carrying tube structure encased in a foamed molded part. Again, the disadvantage of this is that the entire carrying structure is heavy.
A very light design, which is adaptable to smaller mirrors, is taught by DE 44 29 604 A1. In this case, the tube construction is fully dispensed with and the foam element itself remains as the support structure. For this purpose, a gradiated foam is employed as a one-piece element or the element can be composed of several shells.
It is thus the objective of the present invention to make available a sufficiently stable rearview mirror which also offers the greatest possible reduction in vibration.
The achievement of this objective is accomplished by the features of the invention.
Since a blown, hollow plastic body, originating from a plastic blank, is used as a carrier, the result is a very light structure so that even in the case of a cantilevered mirror, or outboard carrier construction, the basic rigidity of the plastic hollow body assures a sufficient stability. At first, it appears doubtful that a blown plastic hollow body would exhibit sufficient stability to be used as a carrier for a rearview mirror arrangement for commercial vehicles. However, by means of the substantial reduction in the weight, the demands for achieving stability are likewise reduced, so that a blown plastic hollow body does indeed offer sufficient stability.
Because of the fact that the plastic blank is made with varying wall thicknesses, the corresponding wall thickness of the finished carrier, that is, the plastic hollow body, can be controlled to specification for location and thickness. That is, the wall thicknesses of the carrier is increased in locations of high stress, i.e. at the point of juncture with the vehicle body, while the thicknesses in zones of lesser stress may be reduced. Also, a grid-like rib structuring on the inner side of the plastic hollow body may be used to increase rigidity.
In accord with a further advantageous embodiment of the invention, the plastic hollow body encompasses a multitude of hollow spaces, which are enhanced by, for instance, inset pieces or correspondingly designed bubble formations. By these measures, the stability is additionally increased and also the possibility exists to fill specified hollow spaces with filling materials.
In accord with another advantageous embodiment of the present invention, the plastic hollow body is constructed in multiple layers, whereby, first, an increased stability is achieved, and second, outer layers can be provided, which are especially smooth and/or acceptable for high quality lacquering.
In accord with a further advantageous embodiment of the invention, the possibility exists of introducing, either in or to the hollow spaces, a stiffening structure whereby the rigidity of the carrier is additionally increased.
In accord with a further advantageous embodiment of the invention, a filling material for the hollow spaces comprises plastic foam, such as polyurethane (PU) foam, a gradient foam or a multi-component hard foam, which binds itself firmly to the inside wall of the hollow spaces and thus increases the stability of the carrier. Moreover, the harmonic vibratory properties of the carrier can be advantageously addressed by the appropriate choice of foam density or its degree of softness, so that during commercial driving the unavoidable vibrations are strongly damped and also as a result, less wear on the mirror assembly is incurred.
Additionally or alternatively, there may be injected into a portion of the hollow spaces, or into various hollow spaces, a viscous fluid mass, for instance a gel or a gelatinous filling material which will also favorably affect specific vibratory and damping characteristics.
In accord with a further advantageous embodiment of the invention, a granulate and/or sand may additionally or alternatively be placed in the hollow spaces. In this way, the fill material can comprise exclusively sand or granulate, or a mixture thereof, or yet a mixture with the above described gel, gelatine or foam. Once again, the stability is favored in a positive way and again the specific vibratory and damping characteristics can be advantageously controlled with attention to specifics.